Note: The recommended alternative to rebuilding your old metal body valve is to install a brand new replacement, such as this one.
A new fuel valve should be completely reliable. A rebuilt metal valve may or may not be 100% since you are reusing the old rubber valve insert. The new o-ring may not seal perfectly in the old valve body. COnsider the cost of a new valve compared to the risk of engine damage or difficult carb turning caused by a poorly functioning fuel valve.
A new fuel valve should be completely reliable. A rebuilt metal valve may or may not be 100% since you are reusing the old rubber valve insert. The new o-ring may not seal perfectly in the old valve body. COnsider the cost of a new valve compared to the risk of engine damage or difficult carb turning caused by a poorly functioning fuel valve.
The fuel selector valve provides several functions.
It is primarily a safety feature and should not be deleted. If the fuel tank air pressure relief check valve sticks closed the excessive fuel tank pressure on a warm day can force fuel past the carburetor seats and flood the engine with liquid fuel. Not only is this a fire and explosion risk but the liquid gasoline can hydraulically lock the engine when you next attempt to start it. Hydro lock can damage the engine internally.
If your model has a three position (7052063 ) fuel selector knob with On - OFF - Reserve settings then the selector valve provides a method of warning you when the fuel tank is getting low (using the ON setting). The engine will run poorly or even stall when the fuel level drops too low. This is your hint to switch to the Reserve setting and head back to the dock for more fuel.
Models with two position (7052151, 7052166) fuel selectors use the display MFD or MFI to warn of Low Fuel. There is no Reserve setting, just ON and OFF.
Since the entire fuel supply is under suction from the tank to the fuel pump inlet it is important that the fuel selector valve be air tight. If the valve leaks air into the fuel supply then the fuel pressure and fuel volume delivered to the carburetors is reduced. Reducing the fuel delivery to the carburetors is a recipe for lean burn and engine damage.
The most common place for air leaks is at the 0-ring that seals the valve shaft into the valve body. Here is the method for removing the old o-ring, cleaning the selector valve and rebuilding it with a fresh o-ring.
This fuel selector valve is ready to be re-assembled. Internally clean, lubricated with 2-stroke oil, new o-ring installed.
The actual 'valve' is this rubber end piece which aligns with the hole in the side of the shaft. When you turn the valve knob the metal shaft aligns with one rubber hole, the other hole, or in between. In between is the OFF valve position.
Note the scratches on the metal valve body. These are from metal burrs around the 3mm retaining screw threaded hole when the valve core was wiggled out.
You can clearly see the semi-circular groove where the retaining screw engages the valve core to keep it in place.
Down inside the valve body are two metal ridges which align with the rubber piece. Typically the rubber piece may be stuck down in there. It is fragile and not available as a separate part. If it will not come out easily without damaging it, just leave it in there and clean things as best you can.
The old o-ring is on top, the new one below.
Notice the cracks in the old o-ring, on the left.
As a new replacement I used a slightly smaller and thicker o-ring than OEM
70 Buna-N, Size AS568A-011
McMaster-Carr 9452K19
There may be a more exact fit Metric o-ring size. I shall update when/if I find one.
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